Modern integrated circuits (ICs) use dielectric layers to isolate the individual devices on a chip from conductive interconnections connected to the individual devices to integrate devices and send and receive signals external to the chip. Popular types of representative dielectric materials include silicon dioxide (SiO2), silicon nitride (Si3N4), phosphosilicate glass (PSG), silicon carbide (SiC), fluorinated silicate glass (FSG), carbon doped oxide (CDO), and cubic boron nitride (CBN). For instance, a dielectric layer of the representative dielectric materials above may be formed at one or more layers of an integrated circuit during integrated circuit fabrication.
The dielectric constant of a dielectric material generally describes the parasitic capacitance of the material. As the parasitic capacitance is reduced, the cross-talk (e.g., a characterization of the electric field between adjacent interconnections, such as aluminum alloy or copper interconnections formed in trenches along the dielectric) is reduced, as is the resistance-capacitance (RC) time delay and power consumption (e.g., with respect to signals conducted along such interconnections).
The dielectric constant of a dielectric material can be substantially effected by water or liquid absorbed in the pores of the dielectric material. Thus, the porosity of the dielectric material, and amount of moisture in those pores can cause a significant increase in the dielectric constant. The porosity of dielectric material is defined as the percent of the volume of dielectric material that is pore space or, in other words, as the ratio of the volume of all the pores in the dielectric material to the volume of the whole dielectric material.